1. Field of the Invention
The present invention relates to a mold and a molding method.
2. Description of the Related Art
As a mold capable of manufacturing a product such as a digital camera and a telescopic lens which requires machining with extremely high accuracy, for example, a mold, as shown in FIG. 9, has been known which has a cavity between a first half 600 and a second half 700, and such a product is injection-molded in the cavity (see, for example, Japanese Published Patent Application No. 2003-231159, paragraphs 0020-0029, FIG. 1).
The first half 600 includes an insert member 610 forming a cavity surface 610a; a body member 620 for holding the insert member 610 from outside and having a tapered protrusion 621 on an end face thereof on the side of the second half 700, and a ball retainer 630 interposed between the insert member 610 and the body member 620. The second half 700 includes an insert member 710 forming a cavity surface 710a; a body member 720 for holding the insert member 710 from outside and having a reversely tapered part 721 on an end face thereof on the side of the first half 600; and a ball retainer 730 interposed between the insert member 710 and the body member 720.
In the mold described above, the interposition of the ball retainers 630, 730 enables the center axis alignment between the insert member 610 and the body member 620 and between the insert member 710 and the body member 720 respectively, and, in the meantime, the use of the tapered protrusion 621 and the reversely tapered part 721 enables the center axis alignment between the first half 600 and the second half 700.
In determining a performance of a lens as a product molded in such a mold, it is extremely important that a center axis alignment is achieved between an optical surface of the lens and a flange integrally molded with the optical surface around the same. In other words, it is desired that the center axis alignment is achieved between the insert member 610 providing the optical surface and the body member 620 providing the flange. If the center axis alignment is not achieved between the optical surface and the flange, namely, between the insert member 610 and the body member 620, an eccentricity of the lens can easily occur, leading to performance deterioration and a cost increase of the same.
In the meantime, the conventional mold described above has problems as follows. When the insert member 610 and the insert member 710 are joined together, it is necessary but troublesome to insert the insert member 610 into the body member 620, for example, while adjusting a positional relation between the ball retainer 630 and the insert member 610 so that the ball retainer 630 be provided in a predetermined position.
Another problem is that, though depending on tolerance or rigidity of the ball retainer 630, an eccentricity of the insert member 610 may occur, making it difficult to achieve the center axis alignment between the insert member 610 and the body member 620.
The present invention is made in the light of the above-mentioned problems, and it is desirable to provide a mold and molding method whose insert member can be smoothly joined together with a body member, whose center axis alignment can be easily performed, and with which a high-quality product can be manufactured.